Some conventional butt-jointed decorative boards are composed of plural small decorative board parts which are butt-jointed to each other, but these are constructed by merely butting the edges of the decorative board parts in the longitudinal direction and jointing the same, or alternatively, a tongue is formed on one edge of the respective decorative board parts in the longitudinal direction while a narrow and long groove is formed on the other edge of the said board parts, the said groove being able to be engaged with the tongue of a different decorative board part, and the decorative board parts thus having the said tongue and groove are merely jointed in the tongue and groove parts.
However, since these conventional merely butt-jointed decorative boards do not have flexibility or bendability, these are defective in the point that the joints are often released to give gaps between the jointed parts when the decorative board is directly applied to a floor with an uneven surface such as a concrete floor, etc. If the board is tried to be applied to such uneven floor so as to give no gaps between the jointed parts, the work would be extremely difficult and, as a result, further gaps would be formed by the application of the board.